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Oranmore, Ireland

Toenshoff E.R.,University of Vienna | Mitchell S.O.,Vet Aqua International | Mitchell S.O.,Trinity College Dublin | Steinum T.,Norwegian Veterinary Institute | And 3 more authors.
PLoS ONE | Year: 2012

Epitheliocystis, a disease characterised by cytoplasmic bacterial inclusions (cysts) in the gill and less commonly skin epithelial cells, has been reported in many marine and freshwater fish species and may be associated with mortality. Previously, molecular and ultrastructural analyses have exclusively associated members of the Chlamydiae with such inclusions. Here we investigated a population of farmed Atlantic salmon from the west coast of Norway displaying gill epitheliocystis. Although 'Candidatus Piscichlamydia salmonis', previously reported to be present in such cysts, was detected by PCR in most of the gill samples analysed, this bacterium was found to be a rare member of the gill microbiota, and not associated with the observed cysts as demonstrated by fluorescence in situ hybridization assays. The application of a broad range 16 S rRNA targeted PCR assay instead identified a novel betaproteobacterium as an abundant member of the gill microbiota. Fluorescence in situ hybridization demonstrated that this bacterium, tentatively classified as 'Candidatus Branchiomonas cysticola', was the cyst-forming agent in these samples. While histology and ultrastructure of 'Ca. B. cysticola' cysts revealed forms similar to the reticulate and intermediate bodies described in earlier reports from salmon in seawater, no elementary bodies typical of the chlamydial developmental cycle were observed. In conclusion, this study identified a novel agent of epitheliocystis in sea-farmed Atlantic salmon and demonstrated that these cysts can be caused by bacteria phylogenetically distinct from the Chlamydiae. © 2012 Toenshoff et al. Source


Fringuelli E.,Agri Food and Biosciences Institute of Northern Ireland | Savage P.D.,Agri Food and Biosciences Institute of Northern Ireland | Gordon A.,Agri Food and Biosciences Institute of Northern Ireland | Baxter E.J.,University College Cork | And 2 more authors.
Journal of Fish Diseases | Year: 2012

The development and the application of a quantitative real-time PCR for the detection of Tenacibaculum maritimum are described. A set of primers and probe was designed to amplify a 155-bp fragment specific to the T. maritimum 16S rRNA gene. The test was shown to be very sensitive, able to detect as little as 4.8 DNA copies number μL -1. In addition, the assay was found to have a high degree of repeatability and reproducibility, with a linear dynamic range (R 2=0.999) extending over 6 log 10 dilutions and a high efficiency (100%). The assay was applied to DNA samples extracted from 48 formalin-fixed paraffin-embedded (FFPE) Atlantic salmon, Salmo salar, gill tissues showing varying degrees of gill pathology (scored 0-3) and from 26 jellyfish samples belonging to the species Phialella quadrata and Muggiaea atlantica. For each sample, the bacterial load was normalised against the level of the salmonid elongation factor alpha 1 (ELF) detected by a second real-time PCR using previously published primers and probe. Tenacibaculum maritimum DNA was detected in 89% of the blocks with no signs of gill disease as well as in 95% of the blocks with mild-to-severe gill pathology. Association between bacterial load and gill pathology severity was investigated. T. maritimum DNA was detected at low level in four of the 26 jellyfish tested. © 2012 Blackwell Publishing Ltd. Source


Fringuelli E.,Agri Food and Biosciences Institute of Northern Ireland | Gordon A.W.,Agri Food and Biosciences Institute of Northern Ireland | Rodger H.,Vet Aqua International | Welsh M.D.,Agri Food and Biosciences Institute of Northern Ireland | Graham D.A.,Agri Food and Biosciences Institute of Northern Ireland
Journal of Fish Diseases | Year: 2012

The development and the application of a quantitative duplex real-time PCR for the detection of Neoparamoeba perurans and the elongation factor α 1 gene (ELF) of Atlantic salmon, Salmo salar L., and rainbow trout, Oncorhynchus mykiss (Walbaum), are described. A set of primers and probe was designed to amplify a 139-bp fragment specific to the N. perurans 18S rRNA gene. The test was shown to be very sensitive, being able to detect as little as 13.4 DNAcopies per μL corresponding to 0.15fg of template DNA. In addition, the reaction that detected N. perurans was found to have a high degree of repeatability and reproducibility, to have a linear dynamic range (R2=0.999) extending over 5 log10 dilutions and to have a high efficiency (104%). The assay was applied to DNA samples extracted from 48 formalin-fixed, paraffin-embedded (FFPE) salmon gill tissues showing varying degrees of gill histopathology and amoebic gill disease (AGD)-type histopathology ranging from absent to severe (each scored 0-3). Neoparamoeba perurans DNA was detected in all the blocks where AGD-type histopathology was diagnosed microscopically and in 43.6% of the blocks showing signs of gill pathology. The association between parasitic load and gill histopathology and AGD-type histopathology severity was also investigated. This study also describes the development and the application of a second real-time PCR for the generic detection of Neoparamoeba spp., Page, 1987. A set of primers and probe conserved among the Neoparamoeba spp. was designed to amplify a 150-bp fragment within the 18S rRNA gene. Applied to N. perurans-negative gill tissues, the method was used to exclude the presence of other Neoparamoeba spp. in those blocks where gill pathology was observed microscopically. © 2012 Blackwell Publishing Ltd. Source


Oldham T.,University of Tasmania | Rodger H.,Vet Aqua International | Nowak B.F.,University of Tasmania
Aquaculture | Year: 2016

Amoebic gill disease (AGD), first documented thirty years ago in sea-caged salmonids, is an ever increasing global concern in finfish aquaculture. The result of gill infection by Neoparamoeba perurans, clinical AGD has been observed in fourteen countries distributed across six continents and in fifteen species of finfish. The greatest impacts of AGD have been on farmed Atlantic salmon during the seawater grow-out phase. When left untreated AGD has resulted in up to 80% mortality, and even mild infections reduce production performance and fish welfare. This review summarizes and analyses three decades of AGD research and outbreaks, with focus on the causal triad of pathogen, host and environment. Statement of relevance: This review provides an improved understanding of AGD including practical applications. © 2016 Elsevier B.V. Source


Baxter E.J.,University College Cork | Rodger H.D.,Vet Aqua International | McAllen R.,University College Cork | Doyle T.K.,University College Cork
Aquaculture Environment Interactions | Year: 2011

Jellyfish have been implicitly linked to a number of fish kill events in marine-farmed finfish over recent decades. However, due to insufficient data, it is difficult to identify small hydrozoan jellyfish as the causative agents of the more common and chronic problem of gill disorders. Gill disorders (physical, pathogenic or parasitic damage to the gills) can be caused by a number of waterborne agents and are an increasing though poorly understood problem for the aquaculture industry. Hence, the first year-long monitoring programme to study hydrozoan jellyfish, other gelatinous zooplankton, phytoplankton and fish health was initiated at 2 aquaculture sites on the west coast of Ireland. At the southern site, 2 jellyfish species previously implicated in aquaculture fish kill events (Muggiaea atlantica and Solmaris corona) occurred at high abundances (combined density of ~450 jellyfish m-3, an order of magnitude lower than during previous mass mortality events). The fish at this site exhibited clinically significant gill damage throughout the peak in jellyfish abundance. Analyses revealed a significant positive correlation between daily fish mortality and the abundance of these jellyfish but not with any other factors. At the northern site, there were low abundances of jellyfish; nevertheless, gill damage due to the protozoan parasite Trichodina sp. was observed over a shorter time period. As the European aquaculture sector experiences annual economic losses due to gill disorders, these findings raise concerns for the expected growth of the industry, especially as jellyfish populations are predicted to increase in some areas. Therefore, mitigation methods need to be developed and implemented. © Inter-Research 2011. Source

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